As the others said. Yes, I haven't heard of Disneyland ever being closed on Christmas. I don't know the exact hours of operation on that day though. If go... have a GREAT time!
They'll be open. In three more days you can check the mobile app for specific operating hours: it only shows through the 22nd at the moment.
I don't work at Disney. But I have an Signature pass without any blackouts so I will be there for Christmas. You might want to call Disney to see they'll be open.
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